"Unidecode" functionality in Emacs

"Unidecode" functionality in Emacs

[John Mastro]

There are "Unidecode" packages for Perl[1], Python[2], and Emacs[3]
(derived from one another in that order). They each transliterate
Unicode text to ASCII, e.g.:

    (unidecode "Déjà vu")
    ;=> "Deja vu"
    (unidecode "北亰")
    ;=> "Bei Jing "

Does Emacs have equivalent functionality built-in?

[ The context for this is that I recently submitted a change to the
  MELPA recipe, and Steve Purcell mentioned[4] that he would be
  surprised if Emacs doesn't already have such functionality. ]

Thanks for any pointers

        John

[1]: http://search.cpan.org/~sburke/Text-Unidecode-1.30/lib/Text/Unidecode.pm
[2]: https://pypi.python.org/pypi/Unidecode
[3]: https://github.com/sindikat/unidecode
[4]: https://github.com/melpa/melpa/pull/5351#issuecomment-373966218

Re: "Unidecode" functionality in Emacs

[Teemu Likonen]

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John Mastro [2018-03-19 15:04:29-07] wrote:

> There are "Unidecode" packages for Perl[1], Python[2], and Emacs[3]
> (derived from one another in that order). They each transliterate
> Unicode text to ASCII, e.g.:
>
>     (unidecode "Déjà vu")
>     ;=> "Deja vu"
>     (unidecode "北亰")
>     ;=> "Bei Jing "
>
> Does Emacs have equivalent functionality built-in?

I don't know of any built-in functions but external "iconv" tool can do
similar thing for Latin scripts. Here's an example Emacs Lisp function
wrapper for "iconv":

    (defun tl-ascii-translit (string)
      (with-temp-buffer
        (insert string)
        (call-process-region (point-min) (point-max)
                             "iconv" t t nil "-t" "ASCII//TRANSLIT")
        (buffer-substring-no-properties (point-min) (point-max))))

Works for Latin scripts:

    (tl-ascii-translit "Déjà vu") ;=> "Deja vu"
    (tl-ascii-translit "北亰") ;=> "??"

-- 
/// Teemu Likonen   - .-..   <https://keybase.io/tlikonen> //
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Re: "Unidecode" functionality in Emacs

[Eli Zaretskii]

> From: Teemu Likonen <tlikonen@iki.fi>
> Date: Tue, 20 Mar 2018 06:59:34 +0200
> Cc: Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
> 
> I don't know of any built-in functions but external "iconv" tool can do
> similar thing for Latin scripts. Here's an example Emacs Lisp function
> wrapper for "iconv":
> 
>     (defun tl-ascii-translit (string)
>       (with-temp-buffer
>         (insert string)
>         (call-process-region (point-min) (point-max)
>                              "iconv" t t nil "-t" "ASCII//TRANSLIT")
>         (buffer-substring-no-properties (point-min) (point-max))))
> 
> Works for Latin scripts:
> 
>     (tl-ascii-translit "Déjà vu") ;=> "Deja vu"
>     (tl-ascii-translit "北亰") ;=> "??"

The iconv's "TRANSLIT" is not the transliteration that's sought here.
It's an attempt to present similarly-looking characters when the
original character is not in the target character set (ASCII in the
above snippet).  So it's a small wonder this only works for European
scripts, because no ASCII character can ever "look like" characters in
other scripts.

Re: "Unidecode" functionality in Emacs

[Eli Zaretskii]

> From: John Mastro <john.b.mastro@gmail.com>
> Date: Mon, 19 Mar 2018 15:04:29 -0700
> 
> There are "Unidecode" packages for Perl[1], Python[2], and Emacs[3]
> (derived from one another in that order). They each transliterate
> Unicode text to ASCII, e.g.:
> 
>     (unidecode "Déjà vu")
>     ;=> "Deja vu"
>     (unidecode "北亰")
>     ;=> "Bei Jing "
> 
> Does Emacs have equivalent functionality built-in?

It's possible to remove accents (the first example) using the
functionality in ucs-normalize.el.  Some transliteration is possible
for scripts for which there exists a "transliteration" input method,
using the code by Michael Welsh Duggan posted here:

  http://lists.gnu.org/archive/html/emacs-devel/2018-02/msg00387.html

For example, you can transliterate Cyrillic text using the
cyrillic-translit input method that comes with Emacs.  But there are
no general-purpose transliteration capabilities in Emacs, AFAIK.

However, it looks like the Perl package is just a huge database of
precomputed transliterations, in which case doing the same in Emacs
Lisp should be almost trivial.

Re: "Unidecode" functionality in Emacs

[John Mastro]

Eli Zaretskii <eliz@gnu.org> wrote:
>> There are "Unidecode" packages for Perl[1], Python[2], and Emacs[3]
>> (derived from one another in that order). They each transliterate
>> Unicode text to ASCII, e.g.:
>>
>>     (unidecode "Déjà vu")
>>     ;=> "Deja vu"
>>     (unidecode "北亰")
>>     ;=> "Bei Jing "
>>
>> Does Emacs have equivalent functionality built-in?
>
> It's possible to remove accents (the first example) using the
> functionality in ucs-normalize.el.  Some transliteration is possible
> for scripts for which there exists a "transliteration" input method,
> using the code by Michael Welsh Duggan posted here:
>
>   http://lists.gnu.org/archive/html/emacs-devel/2018-02/msg00387.html
>
> For example, you can transliterate Cyrillic text using the
> cyrillic-translit input method that comes with Emacs.  But there are
> no general-purpose transliteration capabilities in Emacs, AFAIK.

Thanks, I'll take a look at those.

> However, it looks like the Perl package is just a huge database of
> precomputed transliterations, in which case doing the same in Emacs
> Lisp should be almost trivial.

Yep, that's how the Emacs package works too. It boils down to 25 lines
of Lisp[1] plus the database[2].

Thanks

        John

[1]: https://github.com/sindikat/unidecode/blob/5502ada9287b4012eabb879f12f5b0a9df52c5b7/unidecode.el#L56-L82
[2]: https://github.com/sindikat/unidecode/tree/5502ada9287b4012eabb879f12f5b0a9df52c5b7/data

Re: "Unidecode" functionality in Emacs

[Stefan Monnier]

> However, it looks like the Perl package is just a huge database of
> precomputed transliterations, in which case doing the same in Emacs
> Lisp should be almost trivial.

This said, Emacs comes with several of those databases already in the
form of quail input methods and unicode char metadata, so it should be
possible to get something a bit less trivial which doesn't require any
extra database.


        Stefan